Process of preparing animal skins for tanning



Patented Sept. 15, 1931 1,8223%8 UNITED STATES PATENT orrica EDWARD J'. MAGUIRE, F BROOKLYN, NEW YORK, ASSIGNOR TO THE GRASSELLI CHEML GAL COMPANY, OF CLEVELAND, OHIO, A CORPORATION OF DELAWARE PROCESS OF PREPARING ANIMAL SKINS FOR TANNING No Drawing. Application filed January 24, 1930. Serial No. 423,268.

Animal skins or hides are before tanning solution, freely rinsed in water and are ready submitted to a number of treatments, which, for subsequent processing. The equipmentamong others, are intended to remove from found innormal beam house practice, such the skins and hides such substances or flesh as pits, paddle Wheels, etc., can be conven- I i p tissues which would interfere with the pro iently used in my novel process. The special as duction of leather. apparatus designed for extracting the skins All skins contain substantial amounts of with organic solvents is also easily converted natural greases and fats, which, particularly for application of my novel process,'it being in the case of sheep skins are not removed understood that no distillation and recovery 10 in the dehairing, liming, bating, etc. operof the solvent is required. so ations, and such skins'are before tanning The tri-sodium phosphate treatment when usually submitted to a special degreasing applied to pickled skins depletes somewhat process. The common degreasing processes the skins and loosens the fibres, which is deconsist in treatments with organic fat solsirable in producing certain kindslof sheepvents, such as naptha, carbon-tetrachloride skin leather, such as used for Wearing apes and kerosene oil or others. parel. This de leting effect of the tri-sodiuln I'have found that the natural greases and phosphateon sliins intended to be made into fats associated with animal skins can be reheavier leather can be corrected by a light moved by treating the skins with an aqueous sulfuric acid,.sodium chloride pickle followsolution of tri-sodium phosphate. The ing the degreasing operation. The depleting 78 greases andfats are emulsified or otherwise effect can, to a certain extent, be prevented dissolved in the aqueous solution and are n or diminished by adding sodium chloride to this manner removed from the skins. It 1s the degreasing tri-sodium bath.

possible to recover, as will be explained be- The spent tri-sodium phosphate solution is low, the greases and fats, and particularly usually discarded, but if desired, the fats and 7 wool grease from the aqueous grease and fat greases or soaps can be recovered as such, or emulsions or solutions obtained. My invenin the form of fatty acids by acidifying the tion is particularly adapted to the treatment spent solution. of any animal skin which after processing The amount of solution needed is convert requires the skin to befree of grease, such as iently figured atbetween to 1 gallon per 80 the skins from sheep, goats, rabbits or other 20 pounds of hide. This is, of course, not small animals. critical. It is to a certain extent dependent The dehaired skins are easily and elfec-. upon the type of equipment used, the condi tively degreased by means of an aqueous trition of the' hides and other factors entirely sodium phosphate bath, which is applied to independent of. the principle of the action. of the pickled skins direct, preliminary to tanthe tri-sodium phosphate.- In a similar way ning. j the concentration of the solution,'the tem- In performing the novel process of my inperature, and the duration of the action are vention I prepare an aqueous tri -sodium interdependent and can be varied within very phosphate solution containing, for instance, wide limits Without departing from the spirit from about to about 3% tri-sodium phosof my invention. It will be understood that phate dodecahydrate or equivalent amounts good agitation, increased temperature and of other hydrates. The skins are steeped increased concentration within the conditions therein for several hours at a temperature limited by a maximum of about 3% tri-soranging from about 70 to about F. It dium phosphate concentration and about 110 5 will, of course, be understoodby those skilled F. will speed upth'e degreasing action; On in the art that the use of higher temperature the other hand concentrations below can might injure the skins themselves. The skins be used if suflicientsolution is applied to the are then taken out of the bath, if desired, skins, and the solution be given ample time 60 passed on to rollers to squeeze out the excess to act. As a rule, the specific conditions under which my novel process is applied will have to be adjusted to the practice of and equipment available at the particular factory where this process is adopted.

While it is not customary to degrease heavy, dehaired calf or steer hides before tanning, I found that my novel process is also applicable to this type of hides, and will remove such grease or fat associated therewith, and in this manner avoid any treatment which might be necessary on the tanned leather if the dehaired skins had contained fats or greases. For this type of skins I use substantially the same concentrations, temperatures and other conditions as on sheep or other like, dehaired skins, but I prefer to add water soluble mineral salts to the tri-sodium phosphate bath to counteract the depleting or swelling action of the degreasing agent. Common salt, Glaubers salt, Epsom salt, barium chloride and other similar substances were found convenient for this purpose. The concentration of these salts in the tri-sodium phosphate bath is not very critical and depends upon the plumping action desired. It can vary from a few per cent to saturation of the bath.

Tri-sodium phosphate in aqueous solution has a similar degreasing action on animal skins with hair or wool attached, and produces at the same time a loosening of the wool or hair. This loosening effect is, however, in most instances insufficient to allow of a practical removal of the hair and wool and I prefer therefor to use other depilatories and degrease the skins with tri-sodium phosphate after they have been dehaired; which operation can be proceeded with at any stage before tanning.

The plumping action which tri-sodium phosphate shows on skins immersed in its aqueous solutions can also be made use of to soften or soak salted skins before they are submitted to depilation. A fraction of a per cent of tri-sodium phosphate added to the soak produces in a very short time a soft, pliable stock which is in a very desirable condition for further treatments. The conditions in such a soaking operation are so mild that very little degreasing takes place and the skins soaked in a very light tri-sodium phosphate will have to be submitted to a special degreasing operation after dehairing.

I claim:

1. In a process of preparing animal skins for tanning the step of steeping said skins in an aqueous solution of tri-sodium phosphate.

2. In a process of preparing animal skins for tanning the step of steeping the dehaired skins in an aqueous solution of tri-sodium phosphate.

, 3. In a process of preparing animal skins for tanning the step of steeping the dehaired skins in an aqueous bat-h containing tri-sodium phosphate in an amount equivalent to from about. to about 3% of the weight of the bath .of tri-sodium phosphate dodecahydrate.

4. In a process of preparing animal skins for tanning the step of steeping the dehaired skins at a temperature of from about to about 110 F. in an aqueous bath containing tri-sodium phosphate in an amount equivalent to from about to about 3% of the weight of the bath of tri-sodium phosphate dodecahydrate.

5. The process of degreasing sheep skins which comprises steeping said skins before lgauging in an aqueous tri-sodium phosphate 6. In a process of preparing sheep skins for tanning the step of steeping the skins, freed from wool in an aqueous bath at about 70 to 110 F. containing tri-sodium phosphate in an amount equivalent to about to 3% trisodium phosphate dodecahydrate.

7. In a process of preparing sheep skins for tanning the steps of steeping the skins freed from wool in an aqueous bath at about 70 to 110 F., containing tri-sodium phosphate in an amount equivalent to about to 8% tri-sodium phosphate dodecahydrate, and, following this operation, giving the skins a slight pickle in a bath containing sulfuric acid. and sodium chloride.

In testimony whereof, I aflix my signature.

EDWARD J. MAGUIRE. 

